The present invention relates to an evaporator suitable for use in a car air conditioner, which is a refrigeration cycle to be mounted on an automobile, for example.
In this specification and appended claims, the upper and lower sides of FIGS. 2, 3, 10, 11, 16, and 17 will be referred to as “upper” and “lower,” respectively.
An evaporator of such a type has been proposed (see Japanese Patent Application Laid-Open (kokai) No. 2009-156532). The proposed evaporator comprises two tube rows juxtaposed in an air-passage direction, each tube row including a plurality of heat exchange tubes which extend vertically and are spaced from one another in a direction perpendicular to the air-passage direction; leeward upper and lower header portions provided on upper and lower sides of the leeward tube row; and windward upper and lower header portions provided on upper and lower sides of the windward tube row. The leeward tube row includes three or more tube groups each composed of a plurality of heat exchange tubes. The windward tube row includes a plurality of tube groups each of which is composed of a plurality of heat exchange tubes and the number of which is one less than the number of the tube groups of the leeward tube row. Each of the leeward upper and lower header portions has sections which are equal in number to the tube groups of the leeward tube row, and the heat exchange tubes of each tube group of the leeward tube row communicate with the corresponding section. Each of the windward upper and lower header portions has sections which are equal in number to the tube groups of the windward tube row, and the heat exchange tubes of each tube group of the windward tube row communicate with the corresponding section. A refrigerant inlet is provided at a section of the leeward upper or lower header portion which section is located at one end thereof. A refrigerant outlet is provided at a section of the windward upper or lower header portion which section is located at an end thereof corresponding to the end where the refrigerant inlet is provided, the windward header portion being located on the same side as the leeward header portion on which the refrigerant inlet is provided. The flow direction of refrigerant within the heat exchange tubes of a farthest tube group of the leeward tube row which is farthest from the refrigerant inlet is the same as the flow direction of refrigerant within the heat exchange tubes of a farthest tube group of the windward tube row which is farthest from the refrigerant outlet. A single path is formed by the above-described two farthest tube groups, which are juxtaposed in the air-passage direction and which are the same in terms of the flow direction of refrigerant within the heat exchange tubes.
The structure of the evaporator disclosed in the publication can restrain an increase in passageway resistance at a final path, which includes a super heat region.
Although the evaporator disclosed in the publication can restrain an increase in passageway resistance at the final path, it has the following problem. Since the total channel sectional area of refrigerant channels of the heat exchange tubes which form the first and second paths decreases, the passageway resistance increases, to thereby cancel out the action of restraining an increase in passageway resistance.
Moreover, in an evaporator of a type as disclosed in the publication, in order to enhance cooling performance, it is demanded to equalize the amounts of refrigerant flowing in the heat exchange tubes of the two tube groups—which are located farthest from the refrigerant inlet and the refrigerant outlet, which are juxtaposed in the air-passage direction and form a single path, and which are the same in terms of the flow direction of refrigerant within the heat exchange tubes.
In order to meet such demand, in one evaporator disclosed in the publication, the leeward farthest section and the windward farthest section are connected together by means of communication means projecting from a heat exchange core portion in the lateral direction. However, in this case, since the communication means projects from the heat exchange core portion in the lateral direction, a dead space is produced when the evaporator is installed.
Another evaporator disclosed in the publication has a following structure. A partition wall is provided between the leeward farthest section and the windward farthest section, and communication holes are formed in the partition wall so as to establish communication between the two farthest sections. The communication holes are formed on the outer side, with respect to the vertical direction, of the end portions of the heat exchange tubes on the side toward the two farthest sections. However, in the case where the two farthest sections are located on the upper side of the heat exchange tubes, the communication holes are located above the upper ends of the heat exchange tubes. Therefore, the refrigerant having flowed into the leeward farthest section flows in a large amount into the heat exchange tubes of the farthest tube group of the leeward tube row due to influence of the gravity. Accordingly, the conventional evaporator is insufficient in terms of the effect of equalizing the amounts of refrigerant flowing in the heat exchange tubes of the two tube groups, which are juxtaposed in the air-passage direction and form a single path, and which are the same in terms of the flow direction of refrigerant within the heat exchange tubes. Meanwhile, in the case where the two farthest sections are located on the lower side of the heat exchange tubes, the communication holes are located below the lower ends of the heat exchange tubes. Therefore, when the flow rate of refrigerant changes, the refrigerant having flowed into the leeward farthest section flows in a large amount into the heat exchange tubes of the farthest tube group of the leeward tube row. Accordingly, the conventional evaporator is insufficient in terms of the effect of equalizing the amounts of refrigerant flowing in the heat exchange tubes of the two tube groups, which are juxtaposed in the air-passage direction and form a single path, and which are the same in terms of the flow direction of refrigerant within the heat exchange tubes.